Two-way radio telephone system



July 31, 1928. 1,678,672

L. ESPENSCHIED ET AL v TWO-WAY RADIO TELEPHONE SYSTEM Original; Filed April 19, 1924 75 7F J1, m zua (Kraut? Circlud J INVENT s La 'm mwyw By 'u/Vfflzmwm MTORNEY Patented July 31, 1928. p

; YEUNIZRFID PATENT o:F;F

LLoYn nsrnnscnrnn, :or norms; HERMAN 'A.. AFFEL, :or' BROOKLYN, AND CLIFFORD in. ANDERSON, or? new. YORK," N."Y., .AssIGNons't'ro AMERICAN" TELEPHONE I AND .ZTEIQEGBKPH COMPANY,.ACGORPGRATIONOF NEWYOBKQ 'IWG' WAY" RADIO TELEPHONE SYSTEM.

llppli'cationlfilbd Apri1f.19,..1924,Seriall No. 707,720. ReneWedSeptember2, 1926.

This invention relates to radiowtra-nsmission; f and more; p arrtlcularly. to arrangements for permitting the carryingron rof a two-way conversationwby radio.

zl-leretoforelit:"hasnloeen quite difficult to carrycon a two-way conversationfiloy radio for; a'znumbei of reasons. wNVherethesame antenna" is BHIPlQYBCl IbOth for transmitting and r-re-ceiving; :it rhas -been vfound impracti cal i to -.loalan-ce .the a transmitting channel against the receiving channel si'ifiici'ently well to wp revent. overloading i the i-receiver with transmittedaenergy. Where wdili'terent r antennee 1 are 2' employed :for atransn'iitting .and receiving and even ewhere different wave le'ngthszare employed, ;the amount ofenergy received I by the r radio receiver 1 from the transmitting: antenna has. been too, great for successful operation .unlessithe transmitting and receiving antennaeaare 'separated by prohibitive "distances; -13EVI1 whe-r-e -.the transmittingrchannel is balanced) against the receiving channel? and different wave :lengths m employed 1 for. transmission rand reception,'-an i'undue zamount :of sending energy findswits wayto the receiver. "Another difficulty thathas been-encountered in all these caseeisi-that -energy received from-1a distant radio station,aiter detection finds its nway hack into :the transmitting channel through the connection to a terminal 1 line and is rerddiate'd. v

In." accordance =with the present invention these ditficultiesnare rover-come by associating voice 'o-perated equipment with *both the transmit-ting: and receiving channels. The voice ope rated "equipment -:asso ciated with the transmitting channel :is arranged" to "disahleP-the: receiving circuitzaand, if the trans.- mi tter *isinormally inoperative,- to render the transmitter operative in response to "voice currents-z impiessedunponz the circuit. Preferably: a.- delay circuit :is: interposed :between the point 5 at nvhiclr the voi ce: :oper'at'ed apparatus; is associated withithe: channel: and the transmitter-- so that. the voice: oontrolle d means :may rper-for1n-=its- :lunctions before the voice current-a reaches the transmitter thus aroidi 11g anywhiatus- :orr-cligpping oflt' of the itirst parti oifithe spcech 'signal. I The voice :operatedi-apparatus associated with the receiver isalikewisewarranged so that it? respon'ds to'i-received radio 'signals to disable it he. tram emitting;circuit-iand; :prevent the :a-e-

ceived voice currents from entering the transmitting circuit to be retransmitted. Preferably a-delayfcircuit Willi beremployed initherecei'ver circuit ata point beyond. the voice responsive apparatus, sothat the latter maypertorm its function before the received voice currents will havehad an opportunity to-enter the transmitting channel.

"The invention will now bezmorefullyuD- derstood from the following description when. read in connection with ,the 'accom panying drawing, Figures 1, 2-and 3 of which illustrate three different. embodiments of the invention. v v 1 Referring to Fig.v 1, a simple form ofthe invention is illustrated. .In; this figure, T designatesan ordinary telephone transmitter connected to. an amplifier ZTA, conventionally ,rcpresented; .This amplifier maybe or any typevwellfknownin the=art. 'O.desig nates a vacuum tubeoscilla'tor. -for supplying the carrier. frequency to rthelantenna AT, and M :is' a vacuum tube modulator having ltSFlll'l-Pllt. associated with. the voice frequency 1 amplifier zTA 1 and having its outputassociated with the oscillator: O in suchva. manner that the 'oscillationsuproduced by the-oscillator 'will be modulated in :accordance with speech. A delay 'circuit'TF is. interposedhetween the amplifier TA and the. modulator M. i This delay; circuit may be any type of: transmission element which will cause. a desired time interval toelapse during-the transmission" ofe a' 'wave from its input terminals to its output terminals. For example, thefdelay circuit mayzbeone of the 'we'll known. types elf-Campbell filters sordesignedas to transmit thedesiredvoice band.

AR designates :the receiving antenna which is coupledwi-th a radio receiving'set RS of any welliknown. type, the receiver R being-associated with theareceiving set in "theusual manner. Voice operated equipment is associatedwith the transmitting circuit between the amplifier'T A and the delay circuit 'TF, =said 'equipment comprising a rectifier-amplifier combination, conventionally indicated at TX, and a voice operated relayz'lfY. o'l he rectifier-amplifier combination may beef any well known type, such as awa'cuum tube amplifier associated with a vacuum tube rectifier, these devices operatingvonc'rtozamplify the voice currents and energized in response to transmitted voice signals it Wlll sliort-clrciut the receiving set RS and change the grid potential of the oscillator 0 so that the grid of the oscillator, which is normally excessively negative,

will have such a negative potential applied thereto as to permit it to generate oscillation.

The operation is as follows: When the transmitter Tis spoken into, voice currents are generated and'amplified by the amplifier TA and then impressed upon the rectifieramplifier combination TX so that a direct current component is produced which operated the voice relay TY. The circuit of the relay 10 is accordingly closed, and at its lower contact said relayvshort-circuits the radio receiver RS. At the same time the upper contact of the relay 10 short-circuits the resistance 11 thereby changing the negative potential on the grid of the oscillator 0 so that the oscillator, which is normally unable to function, will now begin to generate oscillations of the carrier frequency to be transmitted to the antenna AT. In the meantime the voice currents are transmitted from the amplifier TA through the relay circuit TF and. arrive at the modulator M after the relay 1.0 has had an opportunity to function. The voice currents .therefore operate through the modulator M to modulate the oscillations generated by theoscillator O, and the modulated oscillations are trans mitted by the antenna AT without any hiatus or clipping off of the first part of the voice signal. The energy radiated from the transmitting antenna ATto the receiving antenna AR is ineffective to produce any action upon the receiving set RS because said set is short-circuited before any radiation takes place. In receiving signals from a distant station, the relay 10 being normally deenergized, the received signals are impressed directly from the antenna AR upon the radio receiving set, and after being detected the voice currents may be heard in the receiver R. As the receiver'R of the transmitter T has no electrical connection with the transmitter in the case illustrated,

. no difficulty will arise because of the received signals being retransmitted by the transmitting channel. 1

In case, however, the transmitting and re- 'ceiving channels are both associated with a common telephone line, a certain amount of received energy may be passed "into the transmitting channel and reradiated. In order toovercome thisdiffieulty, the circuit may be arranged as shown in Fig. 2 in which L designates an ordinary voice frequency transmission line whichis connectedthrough a hybrid coil 12 with the transmitting channel TL and the receiving channel RL, the line being balanced by a suitable network N so that a'c'ondition approachingYoonjugacy will. exist between the transmitting is supplied with a local source of carrier I current RS so that it operates on the well known homodyne principle. The delay circuits RF and TF may be filters of the Campbell type designed to transmit the desired range of voice frequencies. On the input side of the delay circuit TF is bridgedv a rectifier-amplifier combination TX for operating the voice relay TY. The latter controls a relay 11 which short-circuits the. receiving channel at some suitable point, for example, between the detector D and the delay circuit RF. The relay 11 may also change the tuning of the'antenna A where a different frequency is employed for transmission and reception and the same antenna is used for both purposes. A similar rectifier-amplifier combination RX controlling the voice relay RY is bridgedacrossthe receiving channel upon .the'input side'of the delay circuit RF to control'a'relay' 13, which, in response to a rec'eived'signal, short-cir-.

' cuits the transmitting channel TL.

The operation is as follows: Voice currents incoming from theline L are transmitted through the hybrid coil 12 and are impressed upon the rectifier-amplifier TX to energize the voice operated relay TY. This relay completes the circuit of relay 11, which, at itsJeft-handfront contact, closes a short-circuit for the receiving channel RL between the amplifier RA and the delay cir cuit RF. Relay 11 at its right-hand front contactcloses a circuit including a tuning condenser for changing the tuningof the antenna A so that it will be resonant at the' transmitting frequency rather than at the receiving frequency. While these operations are taking place, the voice currents are transmitted through the delay circuit'TF and after'being amplified by the amplifier TA are impressedrupon the modulator M. A sufficient delay occurs in transmissionthroughthe circuit TF so that the voice currents are not impressed upon the modulator M until after the relay 11 has performed its functions. Any transmitted energy which passes by way of the antenna into the receiving detector D is prevented from being transmitted through the receiving channel of the line L tothe transmittingchannel TL by reason of the short-circuit across .the channel RL. previously described.

The antenna A is normally tuned to the receiving frequency, and when signals are received from a distant transmitting station the received radio frequency isimpressed upon the detector D. so that the voice currents are detected in its output circuit and impressed upon the amplifier RA. After being amplified by the latter, the voice currents pass into the. circuit- .of the rectifieramplifier RX and operate the voice relay RY which closes the circuit of the relay 13. The relay 13' in turn closes a short-circuit for the transmitting channel TL. In the meantimethevoice waves pass through the delay circuit. RF and into the line L. Any component of the voice wave which enters the transmitting channel TL. by reason of unbalance is. ineffective to operatethe radio transmitter because of the short-circuit closed by the relay 18. i

It will. be. observed that in the circuit above described boththe transmitting channel and the receiving channel are normally operative. As soon as tran mission takes place over one of these channels, however, the channel transmitting in the other direction is disabled so that no transmitting energy can. afiectthe receiving circuit and no receiving energy canaffect the radio transmitter. By means. of the delay circuits TF and, RF the, voice operated relays are given time to operate and perform their. functions before the voice wavespass into the circuits beyond the delay circuits.

The; useof a modulator and detector of the balancedjtype, such as is illustrated. in Fig. 2, is; not essential to the proper op eration of the circuit. For example, in Figl 3 the modulator M and oscillator/O are of the type shown. in Fig. 1, and separate an-- tennae'AT and AR. are used for transmitting and receiving respectively. The radio receiving apparatus may comprise the detector I) of the ordinary unbalanced type and an amplifier BA for amplifying the de tected signals. The voice operated relay TY :is arranged toshort-circuit the receiving channel RL, and the voice operated relay RY is arranged toshort-circuit the trans mitting channel TL. and to render the oscillater 0; operative.

The operation lS'aS- follows: Voice currents recewedfrom the line L pass into the channel TL: and operate the rectifier-amplifier combination TX to energize the voice relay TY. The. latter closes the circuit ot the relay 11 which completes the short-circuit for the receiving channel BL between the delay circuit RF and the. detector I).

The relay l1 alsochangesthe potential of.

the oscillator O. in themanner shown in 1 sci-that thegoscillatoiyO generates oscillachannel and radio receiving apparatus in tions. In the meantime the voice currents are passed through the delay circuit TF and arrive at the modulator M after a sufiicicnt delay to permit the relay 11 toperform its functions. Any energy radiated from the transmitting antenna AT to thereceiving antenna AB is without efiectupon the receiving channel because the latteris shortcircuited by relay ll.

When signals arebeingtransmitted from the distant communicating system, they are impressed by the antenna AR upon. the detector I) which detects the voice frequency. component, and this component is amplified by the amplifier RA. The voice. currents are then passed into the rectifienamplitier. RX to operate the voice relay RY, which, in turn, closes the circuit of the relay 13. Relay 1.3 completes a short-circuit across the the Voice currents are transmitted through the delay circuit RF to the line I and any I balance will be without effect because the relay 13 will have short-circuited. thetrans-z mitting channel before such current; can be impressed upon the channel. The operation of the relay 13 in both. Fig. 2 a nd Fig. 3 also prevents received voice currents which are transmitted to the linev L and reflected back by reason of some impedance irregularity from producing any effect in the transmitting channel TL.

It will be obvious that the general prim ciples herein disclose-d may be embodied-in many other organizations widely different from. those illustrated without; departing from the spiritof the invention defined in the following claims.

lVhat is claimed is 1. In a radio system, a radio transmitting channel and a radioreceiving channel, radiotransmitting apparatus in said transmitting said receiving channel, said receiving Cll2111 nel being normally operativelyconditioned to function for receiving purposes,.a transmitting antenna normally conditioned to have signal modulated energy applied thereto by said transmitting channeha voice rcsponsive relay associatedwith said transmit-ting channel and responsive to voice currents to disable said receiving channel, and a delay circuit interposed between said voice responsive relay and said radio-transmitting apparatus to enable said relay to perform its function. before the voice currents are impressed upon said transmitting apparatus.

2. In a radio system, a radio:transmitting channel and a radio receiving channe-hiradiotransmitting apparatus in said transmitting channel and radio receiving apparatus in said receiving channel, said receiving channelv being normally operativelyconditioned.

transmitting channel TL. In the meantime I to function for receiving purpose, a transmitting antennav normally conditioned to have signal modulated energy applied theretoby said transmitting channel, a voice responsive relay associated with said transmitting channel and responsive to voice currents to disable said receiving channel and render said transmitting apparatus operative, and a delay circuit interposed between said voice responsive relay and said radio transmitting apparatus to enable said relay to perform its function before the voice currents are impressed. upon said transmit ting apparatus.

3. In a radio system, a radio transmitting channel and a radio receiving channel, radio transmitting apparatus in said transmitting channel and radio receiving apparatus in said receiving channel, said receiving channel being normally operatively conditioned to function for receiving purposes, a transmitting antenna normally conditioned to have energy applied thereto by said transmitting channel, a voice responsive relay associated with said transmitting channel and responsive to voice currents to disable said receiving channel, a. delay circuit interposed between said voice responsive relay and said radio transmitting apparatus to enable said relay to perform. its function before the voice currents are impressed upon said transmitting apparatus, and a. voice responsive-relay associated with said receiving channel and responsive to detected voice currents for disabling said transmitting channel.

4. In a radio system, a telephone line, a radio transmitting channel and a radio receiving channel associated with said telephone line, radio transmitting apparatus included in said transmitting channel and radio receiving apparatus included in said receiving channel, a transmitting antenna normally conditioned to have energy applied thereto by said transmitting channel, and both of said channels being normally operative, the one to receive and the other to transmit, means responsive to the transmission of currents into said'transmitting channel to disable the receiving channel, and means responsive'to the transmission of currents into said receiving channel to disable said transmitting channel.

5. In a radio system, a telephone line, radio transmitting channel and a radio re ceiving channel associated with said telephone line, radio transmitting apparatus in cluded in said transmitting channel and radio receiving apparatus included in said receiving channel, a transmitting antenna normally conditioned to have energy applied thereto by said transmitting channel,

and both of said channels being normally operatlve, the one 'to receive and the other to transmit, means responsive to voice currents entering said transmltting channel for disabling said receiving channel, and means responsive to detected voice currents in said receiving channel for disabling said transmitting. channel. i

6. In a radio system, a telephone line, a radio transmitting channel and a radio receiving channel associated with said telephone line, radio transmitting apparatus in-- cluded in said transmitting channel and radio receiving apparatus included insaidi receiving channel and both of said channels being normallyoperative, the one to receiveand the other to transmit, means responsive to voice currents entering said transmitting channel for disabling'said receiving channel, and means to delay the transmission of said voice currents to said transmitting apparatus until said receiving channel has-been disabled, means responsive to detected voice currents in the receiving channel for dis-.

apparatus included in said receiving chan' nel, said receiving channel. being normally operatively conditioned to function for receiving purposes, a transmitting antenna normally conditloned to have energy apmeans responsive to currents entering said transmitting channel to disable said receiving channel and render said radio transmitting apparatus operative, and means responsive to currents entering said receiving channel for disabling said transmitting channel. 7

8. In a radio system, a telephone line, a

radio transmitting channel and a radio receiving channel associated therewith, radio transmitting apparatus included in said transmitting channel and radio-receiving apparatus included in said receiving channel, said receiving channel being normally operatively conditioned to function for receiving purposes, a transmitting antenna normally conditioned to have energy applied thereto by said transmitting channel,

means responsive to voice currents entering said transmitting channel for disabling said receiving channel and for rendering said radio transmitting apparatus operative, and means responsive to detected voice currents in said receiving channel for disabling said transmitting channel.

9. In a radio system, a telephone line, a radio transmitting channel and a radio receiving channel associated therewith, radio transmitting apparatus included in said ion plied thereto by said transmitting channel,

transmitting channel and radio receiving ceiving purposes, aqtransmitting antennav normally conditioned .to have energy applied thereto by said transmitting channel, means responsive to voice currents entering said transmitting channel for disabling said receiving channel and rendering said radio transmitting apparatus operative, means to delay the transmission of voice currents to said radio transmitting appzfratus'until: said last mentioned means has functioned, means responsive to voice currents detected in the receiving channel for disabling said transmitting channel, and means to. delay the transmission of voice currents to said telephone line until said last mentioned means has functioned. I

10. In a radio system, a telephone line, a radio transmitting channeland a radio receiving channel associated therewith, radio transmitting apparatus included in said transmitting channel andfradio receiving apparatus included in said receiving channel, said receiving channel being normally operatively conditioned to functionifor-rcceiving purposes, a' transmitting antenna normally conditioned to have energyapplied thereto by said transmitting channel, means responsive to currents entering said transmitting channel ,to disable said receiving channel, and means responsive to currents entering. said receiving channel for disabling said transmitting channel.

11. In a radio system, a telephone line, a radio transmitting channel and a radio re ceiving channel associated therewith, radio transmitting apparatus :included in said transmitting channel and. radio; receiving apparatus included in said receiving-channel, said receiving channel being normally operatively conditioned. to ifunction'for receiving purposes, a transmitting antenna normally conditioned to have energy applied thereto by said transmitting channel, means responsive to voice currents entering said transmitting channel to disable said receiving channel, and means responsive to the voice currents detected in said receiving channel for disabling said transmitting channel.

12. In a radio system, a telephone line, a radio transmitting channel and a radio receiving channel associated therewith, radio transmitting apparatus included in said transmitting channel and radio receiving apparatus included in saidreceiving channel, said receiving channel being normally operatively conditioned to function for receiving purposes, a transmitting antenna normally conditioned to have energy ap plied thereto by said transmitting channel,

means responsive to voice currents entering said transmitting channel to disable said receiving channel, means to delay the transmission of said voice currents to vsaid-radio transmitting apparatus until. said receiving channel has been disabled, means responsive to voice currentsdetected inthe receivingchannel for disabling said transmitting channel, and means to delay the transmission of voice currentsto said telephone line until ,said' transmitting'channel has been disabled. I

13. A two-way signaling system comprising two paths adapted fortransmission in,

opposite directions between two stations, means connecting saidpaths in energy flow relationat each station, means in one path to renderit normally inoperative for transmission, means in the other path forrendering it normally operative for transmission, means whereby signal conveying energy impressed on one of said paths renders the normally inoperativepath operative for transmission and the normally operative path inoperative for transmission, and a delay circuit adapted to delay the round-trip transmission of echo currents until saidoperati-ve path has been made inoperative.

l t. In combination, a loop transmission path, means of one signal characteristic over a portion of said loop, means for transmitting signal waves having a different signal characteristic over the remaining portion} of said loop, biased circuit closers normally respectively rendering one portion operative and the other portion inoperative, signalcontrol means whereby. transmission overthe normally inoperative portion actuates said circuit closers to their respectively alternate positions, and a delaycircuit in said normally inoperative echo and singing efiects while both of said portions are momentarily in operative eon+ dition. V I f 15. A. four-wire radio signaling system comprising a two-wire branch having radio transmitting apparatus associated therewith, a second. two-wire branch having radio irece-iving apparatus associated therewith, means to interconnect said branches at the ends remote from said radio apparatus, means normally rendering one branch operative for transmission, means normally rendering the other branch inoperative for transmission, and signal responsive means for substantially simultaneously rendering said normally operative branch inoperative portion for preventing and said normally inoperative branch operative for transmission. 7

16. A four-wire radio signaling system comprising a two-wire branch having radio ends remote from said radio apparatus, means normally rendering one branch operative for transmission, means normally ren dering the other branch inoperative for transmission, and means responsive to signal conveying currents transmitted over the normally inoperative branch for substantially simultaneously rendering said normally operative branch inoperative and said normally inoperative branch operative "for transmission.

, 17." A four-Wire radio signaling system v comprising a two-Wire branch having radio comprisinga tvvoovir'o branch having radio transmitting apparatus associated therewith, a second two-Wire branch'having radio reapp'aratus associated therewith, means toi interconnect said branches at the ends'rernote from said radio apparatus, ineansnormally rendering one branch'operativetor transmission, means normally rendering the other branch inoperative for transmission, means responsive to signal conveying currents transmitted over the normally inoperative branch for substantially simultaneously rendering said normally operative branch inoperative, and said normal- 157 inoperative branch operativefor transmission, and means for preventing the roundstrip; transmission of echo currents over the-T loop constituted by said tour-Wire circuit during the 'opera-tio'nof said signal operated means. 1

1.9.A four-Wire radlo signaling system comprising a two-Wire branch having radio transi'nitting apparatus associated therewith,

a second two-Wire branch having radio receiving apparatus associated therewith, means to interconnect said branches at the ends remote from said radio apparatus, means normally rendering one branch operative for transmission, means normally rendering the other branch inoperative for transmission, signal responsive means for substantially simultaneously rendering said normally operative path inoperative and said normally inoperative path operative for transmission, and delay circuit means for preventing round-tri p transmission of echo currents over the loop constituted by said four-Wire circuit during the operation of said signal operated means.

20. A four-Wire radio signaling system comprising a two-Wire branch having radio transmitting-apparatus associated therewith, a second two-Wire branch having radio receiving apparatus associated therewith, means to interconnect said branches at the ends remote from said radio apparatus, means normally rendering one branch operative for transmission, means normally rendering the other branch inoperative for transmission, means responsiveto signal conveying currents transmitted over the normally inoperative branch for substantially simultaneously rendering'said normally operative branch inoperative, and said normally inoperative branch operative for transmission, and delay circuit means for preventing round-trip transmission of echo currents over the loop constituted'by said four-Wire circuit during the operation of'said signal operated means. 1 i I a x In testimony whereof, e have signed our names to this specification this 17th day of April, 1924. 1

LLOYD'YESPENSOHIED. HERMAN A. AFFEL. onnrronn N. ANDERSON! 

